Polycarbonate resins are prepared by condensation-polymerization of an aromatic diol such as bisphenol A with a carbonate precursor such as phosgene and have excellent impact strength, dimensional stability, heat resistance and transparency. Thus, the polycarbonate resins have application in a wide range of uses, such as exterior materials of electrical and electronic products, automobile parts, building materials, and optical components.
Recently, in order to apply these polycarbonate resins to more various fields, many studies have been made to obtain desired physical properties by copolymerizing two or more aromatic diol compounds having different structures from each other and introducing units having different structures in a main chain of the polycarbonate.
Especially, studies for introducing a polysiloxane structure in a main chain of the polycarbonate have been undergone, but most of these technologies have disadvantages in that production costs are high, and flame retardance and chemical resistance are deteriorated.
In this regard, the present inventors have found that a copolycarbonate comprising a branched repeating unit as described below can improve flame retardance and chemical resistance while maintaining inherent impact strength and melt index of the copolycarbonate, and completed the present invention.